The present invention relates generally to spacecraft antenna arrangements, and more particularly to a concentric arrangement of multiple spacecraft antennas mounted symmetrically about the yaw axis of rotation of the spacecraft.
A wide variety of spacecraft, such as global positioning system satellites, weather satellites, etc., are in orbit around the Earth. In order to maintain proper orbit and proper communications, many such spacecraft must maneuver while in orbit. However, problems may arise during such maneuvers. Such spacecraft typically have multiple antennas. Those antennas that are not aligned with the yaw axis of rotation or center of gravity of the spacecraft may experience problems.
For example, global positioning system (GPS) satellites are placed in a medium earth orbit (MEO) at an altitude of approximately 20190 kilometers. This provides an orbital period of approximately 12 hours. Some satellite manufacturers require that their GPS satellites perform a yaw maneuver of 180 degrees twice per orbit, or four times per day, in order to keep one side of the spacecraft pointing away from the sun at all times to keep the spacecraft thermally stable. Since the location of the spacecraft antenna is used to compute the coordinates of the receiver, information about the movement of non yaw symmetric antennas must be transmitted to the receiver in order to properly compute the receiver location. This adds significant complexity to the system, both in the spacecraft and in ground terminals.
A need arises for a technique by which spacecraft with multiple antennas can maneuver without disrupting communications or signals and without adding complexity to the spacecraft and/or ground terminals. In particular, a need arises for such a technique for spacecraft having coincident or overlapping frequency band antennas.